Electronic mixer and converter

ABSTRACT

1. An electromagnetic device comprising a non-linear element including a section of an electromagnetic energy transmission system, means to contain an electron gaseous medium within said section and means to produce a magnetic field within said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to couple at least one radio frequency signal to said non-linear element for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the signal applied to said non-linear element, and output coupling means having a predetermined filtering action for extracting from said non-linear element energy of a frequency resulting from said interaction.

United States Patent 191 Goldstein et al.

[451 July 15, 1975 1 1 ELECTRONIC MIXER AND CONVERTER [73] Assignee: International Telephone &

Telegraph Corporation, Nutley, NJ.

221 Filed: Mar.ll, 1952 21 Appl. No: 276,011

[52] US. Cl 325/445; 325/448; 332/51 W [51] Int. Cl. H03b 21/00 [58] Field of Search 178/44, 1 D; 332/51, 57,

332/68, 51 W; 325/448, 445; 321/69 R, 69 W [56] References Cited UNITED STATES PATENTS 2,051,537 3/1936 Wolff 332/57 2.106.770 2/1938 Southworth et a1. 332/57 X 2.505.240 4/1950 Gorn l l 1 1 1 1 332/5 2,532,157 11/1950 Evans 1 333/31 2,573,012 10/1951 Gutter; el al.... 333/31 2748353 5/1956 Hogan 332/51 OTHER PUBLICATIONS Magneto-Optics of an Electron Gas with Guided Microwaves" by Goldstein, Lampert and Heney, published in Vol. 82, No. 6 of the proceedings of the 1.R.E. in June 1951, pp. 956 and 957.

Primary ExaminerMaynard R. Wilbur Attorney, Agent, or FirmJohn T. OHalloran; Menotti J. Lombardi; Alfred C Hill EXEMPLARY CLAIM 1, An electromagnetic device comprising a non-linear element including a section of an electromagnetic energy transmission system, means to contain an electron gaseous medium within said section and means to produce a magnetic field within said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to couple at least one radio frequency signal to said non-linear element for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the signal applied to said non-linear element, and output coupling means having a predetermined filtering action for extracting from said non-linear element energy of a frequency resulting from said interaction.

15 Claims, 5 Drawing Figures FlLTER :FMUL 1 ELECTRONIC MIXER AND CONVERTER This invention relates to electronic mixers and con verters and more particularly to mixers and converters using an electron gas as the nonlinear circuit element.

Frequency mixing or conversion can be accomplished electronically only through the use of a nonlinear circuit element. Heretofore, the nonlinear circuit element most commonly used for mixing ultra-high frequencies has been a crystal. The use of a crystal in the circuit of an ultra-high frequency mixer has the serious disadvantage that its power handling capabilities are small. Crystal operation has, in the past, been confined to r-f power levels low compared to the available r-f power levels, both pulsed and CW, at microwave frequencies. In addition, the problem of manufacturing identically performing crystals of a given type is still largely unsolved.

One of the objects of this invention, therefore, is to provide a mixer and converter capable of being used over a wide range of frequencies and which is completely electronic in operation.

Another object of this invention is to provide a mixer and converter capable of handling high r-fpower levels and which can be easily reproduced in manufacture.

A further object of this invention is to provide an electronic mixer and converter utilizing an electron gas as a nonlinear circuit element.

One feature of this invention is the use of an electron gaseous medium in a substantially uniform magnetic field as the nonlinear circuit element of an ultra-high frequency mixer or converter.

A further feature of this invention is the use of an electron gaseous medium in a substantially uniform magnetic field at the junction of a plurality of r-ftransmission structures, and as waveguides and coaxial lines, for example, to act as a nonlinear circuit element in an electronic mixer or harmonic converter.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of this invention for use as a mixer;

FIG. 2 is a cross-sectional view of another embodiment of this invention for use as a mixer;

FIG. 3 is a cross-sectional view of a third embodiment of this invention for use as a harmonic converter;

FIG. 4 is a cross-sectional view of a fourth embodiment of this invention employing a coaxial transmission system; and

FIG. 5 is a perspective view of a fifth embodiment of this invention employing a waveguide junction.

Referring to FIG. 1 of the drawing, a high level r-f mixer according to the principles of this invention therein shown includes a nonlinear circuit element 1 comprising a section of circular waveguide 2 containing an electron gaseous medium within an envelope 3. The electron gaseous medium may be an electron beam and/or an electron gas produced by a d-c or a-c gas discharge, pulsed or CW, by means of cathode structure 4 and anode 5. Electromagnet 6 provides a substantially uniform unidirectional magnetic field having its lines of force parallel with the axis of the section of circular waveguide 2. Provision may be made for modulating the magnetic field by pulsed d-c or a-c current.

The frequencies to be mixed are propagated through an energy transmission system. here shown as a section of rectangular waveguide 7 and a transducer 8 to match the rectangular input waveguide 7 to the section of circular waveguide 2. The section of energy transmission system 2 may alternately be a smooth (fast) structure or a periodic (slow) structure of any useable cross section such for example as circular, elliptical, rectangular, or square. The envelope 3 containing as one possibility, an electron beam in vacuum or as another possibility an appropriate gas, such as argon, at an appropriate pressure, such as l mm Hg, may fill all or part of the waveguide section 2. Electrons in a magnetic field when subjected to a force transverse to the magnetic field will have an oscillating angular component of motion at a frequency dependent upon the intensity of the magnetic field. This frequency may be termed the electron gyromagnetic frequency.

The one essential condition of the magnetic field direction is that it be transverse to a large component of r-electric field in waveguide section 2. This is true for all devices to be described. Solenoid 6, which provides a substantially uniform unidirectional axial field of an appropriate flux density over the electron gaseous medium contained in envelope 3 satisfies this condition. A permanent magnet with pole piece-areas parallel to a large r-electric field component also satisfies this condition and may therefore be used in lieu or in combination with solenoid 6.

The electron gas medium is nonlinear, i.e., the functional relationship between the applied voltage and resultant current is not represented graphically by a straight line. The nonlinear relationship gives rise to frequencies in the output which are not present in the input. We have found that the addition of the magnetic field provided by solenoid 6 enhances the nonlinear characteristics of the electron-gaseous medium. Due to the nonlinear characteristics, when voltages of two fre quencies f, and f respectively, are impressed, output frequencies will be produced which fall into four groups:

A. Frequencies identical with the two input frequencies,f, and f B. Frequencies which are twice the frequency of each component in the input wave and higher harmonics thereof, that is, 21",, 3f,, and 2f;., 3f

C. A frequency equal to the sum of the two frequencies in the input,f+f and generally frequencies of the form nf,+mf with n and m any choice from n =l,2,3,...andm=l,2,3,...

D. A frequency which is equal to the difference of the two frequenciesjrf and generally frequencies of the form nf mf in the input with n and m any choicefromn=l,2,3,...andm=l,2, 3,...

If the electron gyromagnetic frequency as defined above is substantially equal to the frequency of either of the two input signals or equal to a frequency between the two input signals, the magnetic field intensifies the nonlinear characteristics of the electron gaseous medium, that is, the interaction of electrons with the electric fields of the input r-f signals propagated through the electron gaseous medium in the magnetic field is such as to increase the output r-f powers at those frequencies falling into groups B, C, D above over what they would be in the absence of the magnetic field.

In mixing, the desired output electromagnetic wave has a frequency equal to the difference frequency of the two input signals. This wave is propagated along waveguide 2 in both directions. As will be understood by those versed in this art, in order to prevent propagation of this electromagnetic wave energy back toward the r-f signal source, waveguide system 7 and transducer 8 are so designed that either the output wave, whose frequency is lower than either input frequency, cannot propagate in system 7 (that is, is below the cutoff frequency for system 7) or cannot get past transducer 8 into system 7. The output wave will be propagated through the filter 9 into output waveguide 10. Filter 9 is so designed that its pass band contains the desired frequency. This type of output coupling is useful where the frequency difference frf lies in the microwave region.

Referring to FIG. 2 of the drawing, the alternate form of mixer in accordance with the principles of this invention therein shown includes a nonlinear circuit element 11 comprising a section of rectangular waveguide 12 closed at one end 13, an electron gaseous medium contained within an envelope 14, and an electromagnet 15. The waveguide element 12 may be circular instead of rectangular. Also a permanent magnet may be used in lieu of the electromagnet.

The two frequencies to be mixed are propagated through waveguide 12. Due to the nonlinear characteristics of the electron gaseous medium, which are increased because of the influence of the magnetic field, the output signal will contain an electromagnetic wave having a frequency equal to the difference in frequencies of the two input r-f signals. A coaxial output connector 16 having its inner conductor 17 extending into waveguide 12 is located at any position which is not substantially an integral number of half wavelengths corresponding to either input frequency from the closed end 13 of waveguide 12. The use of coaxial output connector 16 permits the mixing of two input rsignals having a difference in frequency which is too low to be conveniently propagated in waveguide transmission systems. A filter 16a is coupled to the output connector 16 to eliminate all but the desired frequency response from the output signal.

Referring to FIG. 3 of the drawing. a harmonic con verter in accordance with the principles of this invention is shown which includes the nonlinear circuit element 18 comprising a section of rectangular waveguide 19, an electron gaseous medium contained within an envelope 20, and an electromagnet 21. The section of waveguide may be circular instead of rectangular. Also, a permanent magnet may be used in lieu of an electromagnet.

The frequency to be converted is propagated into waveguide 19 by means ofa coaxial input connector 22 having its inner conductor 23 extending into waveguide 19 and located substantially an odd number of quarter wavelengths from the metallic short 24. The electron gaseous medium contained within envelope and under the influence of the magnetic field produced by magnet 21 will act as a nonlinear element. Since the input consists of only one RF signal, the output signal due to the nonlinear characteristics will comprise the fundamental and harmonic frequencies thereof which are propagated in both directions from the nonlinear element into waveguide 19. The output at a particular harmonic of interest may be taken by coupling an energy transmission system 25 to one end of the waveguide 19 through filter 26 which is designed to eliminate all output frequencies below the desired frequency and, if necessary, also those frequencies above the desired frequency.

Referring to FIG. 4 of the drawing, a frequency converter in accordance with the principles of this invention is shown which includes a coaxial transmission line 27, an electron gaseous medium contained between windows 28a and 28b, and an electromagnet 29. The electron gaseous medium is contained within the coaxial transmission line 27 by sealing windows 28a and 28b to the inner conductor 30 and outer conductor 32. The portion 31 of the inner conductor 30 contained between windows 28a and 28b acts as a thermionic cathode. The outer conductor 32 acts as an anode electrode. The tube operates with or without negative po tential applied to the cathode 31. If negative potential is applied, then cathode 31 is electrically insulated from conductor 30. Thermionic emission of electrons from cathode 31 causes an electron cloud to form between the windows 280 and 28b coaxial with the inner conductor 31. A substantially uniform longitudinal magnetic field is impressed on the electron cloud by means ofa magnet 29 to increase the nonlinear characteristics of the interaction of the r-f electric field with the electron gaseous medium contained within envelope 32. The input r-fsignal propagating along the coaxial line 27 travels through the nonlinear element. The output signal will contain electromagnetic waves at the fundamental and harmonic frequencies of the input wave. If the magnetic field is such that the gyromagnetic frequency is substantially equal to the frequency of the input r-f signal, the interaction of the electron gaseous medium with the electric field of the input signal will be particularly nonlinear, causing a maximum of power to appear in the harmonics. Appropriate filter structures 32a are added in the output coupling to eliminate signals of undesired frequency.

Referring to FIG. 5, an ultra-high frequency mixer in accordance with the principles of this invention is shown which includes a section of electromagnetic transmission system comprising a junction of four arms or branches of rectangular waveguides 33, 34, 35, and 36. An electron gaseous medium is contained and controlled within envelope 37 at the junction of the four waveguides. A substantially uniform magnetic field coaxially of arms 35, 36 is impressed on the electron gaseous medium by means of the solenoids 38.

One of the input signals is propagated down waveguide 35 and the other input signal is propagated down waveguide 36. When the gyromagnetic frequency is made substantially equal to the frequency of one of the input rf signals, there is a resonance increase in the nonlinearity of the interaction of the electron gaseous medium with the incident r-ffields and particularly efficient mixing occurs, that is there is then a maximum of r-f power at a frequency equal to the difference in frequency of the two input signals. This output signal at a frequency equal to the difference in frequency of the two input signals is propagated along waveguides 33 and 34 to which appropriate energy transmission structure and filters may be added in arms 35 and 36 to prevent the mixing output power from traveling down these arms. They may also be added in arms 33 and 34 to prevent any signal but the mixing output signal from traveling in these arms.

In accordance with the principles of this invention, the waveguide junction may be formed of only three sections of waveguide into a three-arm section such as a shunt Tee or series Tee. Furthermore, it is not essen tial that the arms of the section all have the same geometric form or cross sectional area. In general, each arm will be designed for the optimum transmission of the signal frequency propagated therethrough and/or the arm may be designed to exclude frequencies that are undesirable.

While we have described above the principles of our invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

I. An electromagnetic device comprising a nonlinear element including a section of an electromagnetic energy transmission system, means, to contain an electron gaseous medium within said section and means to produce a magnetic field within said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to couple at least one radio frequency signal to said nonlinear element for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the signal applied to said nonlinear element, and output coupling means having a predetermined filtering action for extracting from said nonlinear element energy of a frequency resulting from said interaction.

2. A device according to claim 1, wherein said nonlinear element comprises a section of waveguide, an envelope contained Within said section of waveguide, an ionizable medium contained within said envelope, and electrode means to ionize said medium.

3. A device according to claim 1, wherein said non linear element comprises a section of coaxial cable, an envelope coaxial with a section of the inner conductor of said coaxial cable and having its ends sealed to said inner conductor, and means to produce an electron gaseous medium within said envelope.

4. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a section of rectangular waveguide and means to couple said rectangular waveguide to said section of energy transmission system of said nonlinear element.

5. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a section of coaxial cable having its inner conductor extending into said section of energy transmission system of said nonlinear element.

6. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a plurality of waveguide structures joined to said section of said energy transmission system of said nonlinear element.

7. A device according to claim 1, wherein said coupling coupling means includes a section of coaxial Cable having its inner conductor extending into said section of said energy transmission system of said nonlinear element.

8. A device according to claim 1, wherein said output coupling means includes a section of waveguide coupled to said section of said energy transmission system of said nonlinear element.

9. A device according to claim 8, wherein said output coupling means further includes means to eliminate undesirable frequency responses from the output radio frequency energy.

10. An electronic frequency mixer comprising a nonlinear circuit element including a section of electromagnetic energy transmission system, an envelope contained within said section, an ionizable medium contained within said envelope, electrode means to ionize said medium and means to produce a magnetic field in said ionized medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to couple sources of electromagnetic wave energy of different frequencies to said nonlinear circuit for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said nonlinear element, and output coupling means having a predetermined filtering action for extraction from said nonlinear circuit element, energy of a frequency resulting from said interaction.

11. A mixer according to claim 10, wherein said section of energy transmission system of said nonlinear cir' cuit element is closed at one end and said output coupling means includes a section of coaxial cable having its inner conductor extending into said section of energy transmission system.

12. An electromagnetic frequency converter comprising a nonlinear circuit element including a section of electromagnetic energy transmission system, an envelope contained within said section, an ionizable medium within said envelope, electrode means to ionize said medium and means to produce a magnetic field within said ionized medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, a source of radio frequency energy, a coaxial input coupling having its inner conductor extending into said section of energy transmission system to couple said r-fsource to said nonlinear circuit element for interaction with said gyromagnetic frequency therein, said interaction resulting in energies having frequencies absent from the energy applied to said nonlinear element, and output coupling means having a predetermined filtering action for extracting from said non-linear circuit element, energy of a frequency resulting from said interaction.

13. An electromagnetic frequency converter comprising a section of coaxial cable, an envelope coaxial to a section of the inner conductor of said coaxial cable having its ends sealed thereto, an electron gaseous medium contained within said envelope, means to produce a magnetic field within said electron gaseous me dium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, a source of radio frequency energy. means to propagate said radio frequency energy through said electron gaseous medium for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said electron gaseous 7 medium, energy of a frequency resulting from said in-. teraction. J

14. An electronic device comprising a plurality of electromagnetic waveguide elements joined together, means to contain an electron gaseous medium within said junction of said transmission elements, means to produce a substantially uniform magnetic field in said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to propagate radio frequency energy through at least one of said electromagnetic waveguide elements into said electron medium for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said gaseous medium, energy of a frequency resulting from said interaction.

15. An electronic devicepomprising a plurality of electromagnetic waveguide elements joined together, means to contain an electron gaseous medium within said junction of said transmission elements, means to propagate radio frequency energy through at least one of said electromagnetic waveguide elements into said electron medium for interaction with said electron gaseous medium, said interaction resulting in energies having frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said gaseous medium energy of a frequency resulting from said interaction. 

1. An electromagnetic device comprising a nonlinear element including a section of an electromagnetic energy transmission system, means, to contain an electron gaseous medium within said section and means to produce a magnetic field within said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to couple at least one radio frequency signal to said nonlinear element for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the signal applied to said nonlinear element, and output coupling means having a predetermined filtering action for extracting from said nonlinear element energy of a frequency resulting from said interaction.
 2. A device according to claim 1, wherein said nonlinear element comprises a section of waveguide, an envelope contained within said section of waveguide, an ionizable medium contained within said envelope, and electrode means to ionize said medium.
 3. A device according to claim 1, wherein said nonlinear element comprises a section of coaxial cable, an envelope coaxial with a section of the inner conductor of said coaxial cable and having its ends sealed to said inner conductor, and means to produce an electron gaseous medium within said envelope.
 4. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a section of rectangular waveguide and means to couple said rectangular waveguide to said section of energy transmission system of said nonlinear element.
 5. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a section of coaxial cable having its inner conductor extending into said section of energy transmission system of said nonlinear element.
 6. A device according to claim 1, wherein said means to couple at least one radio frequency signal to said nonlinear element includes a plurality of waveguide structures joined to said section of said energy transmission system of said nonlinear element.
 7. A device according to claim 1, wherein said coupling coupling means includes a section of coaxial cable having its inner conductor extending into said section of said energy transmission system of said nonlinear element.
 8. A device according to claim 1, wherein said output coupling means includes a section of waveguide coupled to said section of said energy transmission system of said nonlinear element.
 9. A device according to claim 8, wherein said output coupling means further includes means to eliminate undesirable frequency responses from the output radio frequency energy.
 10. An electronic frequency mixer comprising a nonlinear circuit element including a section of electromagnetic energy transmission system, an envelope contained within said section, an ionizable medium contained within said envelope, electrode means to ionize said medium and means to produce a magnetic field in said ionized medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitUdinal axis of said section, means to couple sources of electromagnetic wave energy of different frequencies to said nonlinear circuit for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said nonlinear element, and output coupling means having a predetermined filtering action for extraction from said nonlinear circuit element, energy of a frequency resulting from said interaction.
 11. A mixer according to claim 10, wherein said section of energy transmission system of said nonlinear circuit element is closed at one end and said output coupling means includes a section of coaxial cable having its inner conductor extending into said section of energy transmission system.
 12. An electromagnetic frequency converter comprising a nonlinear circuit element including a section of electromagnetic energy transmission system, an envelope contained within said section, an ionizable medium within said envelope, electrode means to ionize said medium and means to produce a magnetic field within said ionized medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, a source of radio frequency energy, a coaxial input coupling having its inner conductor extending into said section of energy transmission system to couple said r-f source to said nonlinear circuit element for interaction with said gyromagnetic frequency therein, said interaction resulting in energies having frequencies absent from the energy applied to said nonlinear element, and output coupling means having a predetermined filtering action for extracting from said non-linear circuit element, energy of a frequency resulting from said interaction.
 13. An electromagnetic frequency converter comprising a section of coaxial cable, an envelope coaxial to a section of the inner conductor of said coaxial cable having its ends sealed thereto, an electron gaseous medium contained within said envelope, means to produce a magnetic field within said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, a source of radio frequency energy, means to propagate said radio frequency energy through said electron gaseous medium for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said electron gaseous medium, energy of a frequency resulting from said interaction.
 14. An electronic device comprising a plurality of electromagnetic waveguide elements joined together, means to contain an electron gaseous medium within said junction of said transmission elements, means to produce a substantially uniform magnetic field in said electron gaseous medium to produce an electron gyromagnetic frequency therein, said magnetic field being substantially parallel to the longitudinal axis of said section, means to propagate radio frequency energy through at least one of said electromagnetic waveguide elements into said electron medium for interaction with said gyromagnetic frequency, said interaction resulting in energies having frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said gaseous medium, energy of a frequency resulting from said interaction.
 15. An electronic device comprising a plurality of electromagnetic waveguide elements joined together, means to contain an electron gaseous medium within said junction of said transmission elements, means to propagate radio frequency energy through at least one of said electromagnetic waveguide elements into said electron medium for interaction with said electron gaseous medium, said interaction resulting in energies haVing frequencies absent from the energy applied to said gaseous medium, and output coupling means having a predetermined filtering action for extracting from said gaseous medium energy of a frequency resulting from said interaction. 